The idea of being the primary running back in an offense built for prolific rushing, the thought of running with confidence even when defenses knowing he'll get the ball — these are things he knows well.

After three years of struggling for carries at USF, totaling 400 rushing yards and three touchdowns, Shaw enters his senior year wanting the feeling from his last two years at Arcadia DeSoto County High, when he rushed for a total of 4,935 yards and 64 touchdowns.

"I'm seeing the guy I remember from high school, all that potential," said Bulls coach Willie Taggart, who recruited Shaw when he was head coach at Western Kentucky. "I think Marcus has the capability of becoming the running back we all know he can be."

Shaw had three 300-yard rushing games as a high school senior, and four more with more than 200 yards. As a junior, facing Estero, he rushed eight times for 344 yards, including touchdowns of 72, 44, 80, 40 and 68 yards — all in the first half.

"And I won homecoming king that night," said Shaw, known to teammates as "Squirrel" for his quick, shifty nature and his diminutive frame.

Asked about the challenge of carrying the ball in a power running game like USF wants, Shaw said he likes it better when defenses are coming at him. "It kind of makes it easier," he explains. "People try to go at you harder, get out of their element, and it makes it easier."

USF's coaches have praised a new maturity in Shaw, who grew increasingly frustrated last season, so much so that in the finale, a dismal 27-3 loss to Pittsburgh, he stormed off into the tunnel during the game in an emotional lapse caught by TV cameras. He came back out, but knows that wasn't how he wanted fans to see him.

"I know not to walk off the field like that anymore. All the cameras out there, people probably think I have a bad attitude, which I really don't have," Shaw said.

Asked what set him off, Shaw is blunt about the Bulls' losing record under coach Skip Holtz, including 1-6 marks in the Big East his last two years: "Three years of that," he said. "Three years of nothing."

Shaw is more measured now, careful in words and his actions, remembering the wrong reputation he built early in his USF career.

"I used to just go off my first action, not think about a lot of stuff I do before I do it," said Shaw, who wears No. 20 in tribute to his favorite back growing up, Barry Sanders. "I think before I talk now, make sure I live life the right way, to make my mom proud. I'm really beyond the jokes now. I'm here to play football."

There's an urgency to Shaw, as USF's only offensive player with three letters earned understands this is his last chance.

"I think Marcus Shaw knows this is senior year. This is his year to put up or shut up," running backs coach Telly Lockette said. "His career here has been a little up and down, but he's buying in to what Coach Taggart is trying to get across to the seniors. He's buying into the whole deal, trying to step up and be a leader."

He's not built like Taggart's typical starting running backs, at just 5 feet 9 and 178 pounds. Taggart and his coaches concede they will run "by committee," with junior Mike Pierre and freshmen Darius Tice and Sta'fon McCray contributing.

"For what we run, he's not the prototype guy to run this type of offense," Lockette said. "But he shows toughness. We're going to make it happen with him. He can take it the distance any time."

Thinking of USF's opener this Saturday against McNeese State, Shaw remembers his first game as a Bull, in the 2010 opener against Stony Brook, when he broke loose for a 63-yard touchdown on USF's final play of a 59-14 win. The success was short-lived, as he totaled 28 yards the rest of that season, and 38 his sophomore year. He focused on special teams, where he had 10 tackles.

Now he has a team looking to him to lead a running attack that could be the Bulls' new identity. The defense will come at him, and Shaw is ready to see if can get back to his old ways.